Question

The true statement for the acids of phosphorus, $H_{3}P{O}_2$,
$H_{3}P{O}_3$ and $H_{3}P{O}_4$ is

• A. the order of their acidity is $H_{3}P{O}_4>H_{3}P{O}_3>H_{3}P{O}_2$
• B. all of them are reducing in nature
• C. all of them are tribasic acids
• D. the geometry of phosphorus is tetrahedral in all the three

Answer 1

Answer: (D)

$H_{3}P{O}_2,H_{3}P{O}_3$ and $H_{3}P{O}_4$ contain one, two and three ionisable hydrogen atoms respectively.

$H_{3}P{O}_2\rightleftharpoons H^{+}+H_{2}P{O}_2^{-}$

$H_{3}P{O}_3\rightleftharpoons H++H_{2}P{O}_3^{-}\rightleftharpoons H^{+}+HP{O}_3^{2-}$

$H_{3}P{O}_4\rightleftharpoons H^{+}+H_{2}P{O}_4^{-}\rightleftharpoons H^{+}+HP{O}_4^{2-}$

$\rightleftharpoons H^{+}+P{O}_4^{3-}$

But there is very little difference in acidity.

As P is $s{p}^3$ hybridised in all therefore all are tetrahedral.